Thanks Mike. The coffee was really an espresso
Here are more pictures.
First the Not So Concave Cup:

I really like the shape, but...
- the capacity is quite small (I will measure it in a video)
- it is not so easy to drink into it (in particular, avoid the corners)
- there is always some coffee remaining in the bottom, because the inner shape is closer to a sphere than to half of a sphere
So it is a nice object, but not really functional cup (I know, somebody warned me about that )If someone can find another usage, let me know

This one seems nearly perfect.
- the capacity is not as small and thus it is suitable for an espresso (I will measure it later)
- easy to drink (not coffee leaking or remaining inside)
- the handle does not get too hot
The only drawback I see is that grabbing the hidden handle of the cup when it is on the table is not that easy because the cup is not very high, but I think this is a minor issue.

Unfortunately I have no chicken (and I confess: no egg) to answer with confidence, but I think it is too small.
Perhaps, a way to recycle it would be to cut it at half height and take advantage of the material saved to scale it and make it bigger.

Some times form is over function (I designed a whole line of square drinkware with extreme rejections over usability) What about rounding out two opposite sides? So you have 2 potential handle areas, and 2 potential drinking areas.

I learned a long time ago the wisest thing I can do is be on my own side, be an advocate for myself and others like me. -Maya Angelou
michael@shapeways.com Community Advocate

Thanks Joseng.
Yes, Mike is right, it is a manufacturing requirement. If I had not added this outlined shape the whole bottom face would have been unglazed.
This is very common, and if you check most of your ceramics object, you will notice that they have this kind of line following the shape of the bottom face which remains unglazed.
This being said, for the Identical Twin Cup that I ordered recently, I asked the production team to remove the glaze not only on the bottom but also on a side for symmetry reasons:
I hope they will be able to do it...
I will let you know when I receive it....

Unfortunately, the Identical Twin Cup cannot be printed (it wraps too much). But with the new pricing scheme (and me lowering my markup), all the designs that have previously printed are now at a very attractive price ($29.90 for most of them)!

I believe that the cups that are now $29.90 used to be in the range of $70 before. Once again, the difference is not only the new pricing model but also a lower markup on my side, but all is linked: my markup is very dependent on the manufacturing price. The reason why I am not 100% sure is that I sold none before (except the Moebius Cup which was $66.90 and the Concave Mug which was $69.98). Now that they are really affordable (even less expensive with my markup than what I initially paid for them without my markup), I hope this will change
So here are the models that are now $29.90 (in bold those which have already been successfully printed):
- the Moebius Cup (used to be $66.90)
- the Sphere Cup
- the Whirl Cup
- the Hypersphere
- the Hypercube
- the Flying Cup
- the TriCyl
- the Toroidal Cup
- the Classic Cup
- the Double Cone Cup
- the Double Cylinder Cup